About c : ld—export-dynamic-for-just-one-library

It’s possible to pass --export-dynamic to ld and this will export symbols in the program (so that they are available to any shared libraries loaded at run-time):

$ cat > test.c

void foo() {}

int main() { foo(); }

^D
$ gcc test.c
$ nm -D a.out | grep foo

…nothing. And now:

$ gcc -Wl,--export-dynamic test.c
$ nm -D a.out | grep foo
0000000000001129 T foo

…works.

This is documented in https://sourceware.org/binutils/docs-2.34/ld/Options.html#Options

Is it possible to just export symbols from one particular static library?

Given like:

$ gcc myprogram.cc lib1.a lib2.a lib3.a

Say I just wanted to export symbols in the program from lib2.a, but not lib1.a or lib3.a?

I tried:

$ gcc myprogram.cc lib1.a -Wl,--export-dynamic lib2.a -Wl,--no-export-dynamic lib3.a

but it doesn’t work, it looks like --export-dynamic is global.

(The documentation mentions --dynamic-list=listfile but I didn’t understand the format of the file, or how to extract the symbol list from the static library?)

how to extract the symbol list from the static library?

nm staticlib.a | awk 'some parsing here, mostly {print $3}'

didn’t understand the format of the file

I also don’t, but I’ve found this link: https://sourceware.org/legacy-ml/binutils/2010-01/msg00416.html . The file should contain:

{
   foo;
};

ld –export-dynamic for just one library?

Untested:

gcc myprogram.cc lib1.a lib2.a \
    -Wl,--dynamic-list=<(echo '{'; nm lib1.a | awk '{print $3";"}'; echo '};')